Download What is a Cochlear Implant?

What is a Cochlear Implant?
-A biomedical device that presents an auditory signal
using electrical stimulation of the inner ear.
Source: seattlepi.nwsource.com/ lifestyle/echo28.shtml
Historical Background
•Late 1790’s
-Alessandro Volta performed an experiment which directly
stimulated his own auditory nerve using direct current.
-He described hearing “a kind of crackling or bubbling.”
Historical Background cont...
•1868
-Brenner stimulated the ear using alternating current. He
varied the polarity, intensity, and rate of the stimulus.
-Subjects reported hearing “…strange metallic-like
sounds…”
A Brief Historical Background cont...
•Jump to the 1950’s and 1960’s…
-Experiments performed that directly electrically stimulated
the human cochlear by implanting electrodes in the middle
or inner ear.
-Some hearing percepts were reported, although these
early experimental devices allowed virtually no speech
recognition.
Historical Background cont...
• The 1960’s to the 1970’s: Lots of questions such as...
– How should auditory information (frequency and intensity) be
coded in an implant device?
– It was known that profoundly deaf people lose auditory nerve
cells (spiral ganglion cells). Would this mean an implant wouldn’t
work if there was nothing to stimulate?
– If there were enough spiral ganglion cells to stimulate in a
profoundly deaf person, would the implant physically destroy the
remaining cells?
How Does A Cochlear Implant Work?
Source:http://www.bionicear.org/mhg/cicaboutcochlearimplants.html
How Does a Cochlear Implant Work?
• Microphone/Speech Processor/Induction Coil
Source: www.cochlear.com
How Does a Cochlear Implant Work?
• Electrical pulses are sent to
the metal bands on the
electrode array
•Precisely controlled current
flows between the active
electrode(s) and return
electrode(s)
 Spiral ganglion cells are
stimulated
Source: www.cochlear.com
How Does a Cochlear Implant Work?
• Biphasic current pulses are
used:
• Charge balanced pulses
• Residual current does not
accumulate
• Vital to prevent damage to
inner ear tissue
[insert biphasic pulse]
• Loudness is related to the
total current
• What would pitch be related
to?
• Site of stimulation
Source: www.cochlear.com
Demonstration
Demo by: Bob Shannon, Qian-Jie Fu, John G. Galvin III, House Ear Institute
If you want to know more:
http://www.hei.org/research/depts/aip/audiodemos.htm
Candidacy for Cochlear Implants
• Clinical criteria constantly changing:
– Better speech processing strategies
– Implant technology has improved
• The fundamental question:
– Is a cochlear implant likely to give better performance
than the alternative (hearing aids, doing nothing)?
• Different selection criteria for adults and children
Some Selection Considerations
• Audiological results (pure tone and speech perception testing)
– Compare pre-operative speech perception with those of
implanted people.
• Middle ear pathology
• Post-lingual or pre-lingual deafness
• Age
• Duration of deafness
• Medical contraindications
Candidacy for children
• Different testing techniques:
– Visual reinforcement audiometry (~6 months – 2
years)
– Play audiometry (2 years +)
– Electrophysiological tests (SSEP/ABR/OAE)
• Assessment of communication skills
– Speech and language
• Oral or other language
• Phonology, morphology, syntax, semantics, and pragmatics
• Results are used in conjunction with other tests
The Social Consequences of Implantation
• Views of people in the Deaf Community
– Cochlear implants threaten sign language and
Deaf culture
• What are the advantages/disadvantages
of cochlear implants?
– Social
– Economic